This invention relates to a fuel reservoir apparatus mounted on an automobile for causing fuel vapor within a fuel tank to flow towards a canister.
One known fuel reservoir apparatus of the type under consideration is disclosed in Japanese Patent Unexamined Publication No. 3-267565. In this apparatus, the pressure within a tank is controlled by a check valve of the spring type.
Recently, it has been demanded to keep the pressure within a tank to a lower level, and there has been proposed a mechanism as disclosed in Japanese Utility Model Unexamined Publication No. 4-105959, in which a check valve and a solenoid valve are used in a parallel manner, and the solenoid valve is opened at the time of refuelling (that is, when a filler lid is opened) to keep and control the pressure within a tank to a low level.
However, in the former construction in which the pressure within the tank is controlled only by the check valve of the spring type, the valve opening and closing pressures are determined by a pressure difference between the opposite sides of the valve, and therefore it is difficult to adjust the pressure in a low-pressure condition. Namely, this pressure difference varies in accordance with the resistance of flow through pipes provided on the opposite sides of the valve, an amount of adsorption of fuel vapor by a canister, a variation in an amount of fuel vapor produced in the tank, etc.
In the latter construction, the solenoid valve and the check valve are used in a parallel manner, and even when a pressure within the tank is below a predetermined level, fuel vapor is conducted to a canister via the solenoid valve. However, since the solenoid valve is opened at the time of refuelling, a piping circuit communicates with the ambient atmosphere via the canister, so that a pressure within the tank is not maintained, which leads to the possibility of excessive refuelling.